Dependencies inform how multiple tasks within a project must be sequenced and scheduled.

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Establishing dependencies between multiple tasks in a project plan is an important part of turning a task list into a timeline. Dependencies describe relationships between tasks and inform project managers and team members how tasks need to be sequenced. Projects of every size have dependent tasks and a specific sequence in which some tasks need to be completed.

Spreadsheet.com supports the four types of dependencies found in most project management software programs:

Learn more about each type of dependency in our article Introduction to Dependencies.

Creating Dependencies Between Tasks

You can create dependencies between tasks in a Gantt view’s sheet section, or on the Gantt chart itself. Dependencies are recorded in the worksheet’s Predecessor column, as well as shown on the Gantt chart as lines with arrows. Before creating dependencies, make sure that dependencies are enabled in your worksheet’s Project Management settings.

How to Establish a Dependency Between Two Tasks (in sheet)

1. Click the downward arrow on the right side of a task’s Predecessor column
2. Select the task’s predecessor from the dropdown list of Related row options

When you create a dependency between two tasks, the dates of the dependent task may change automatically depending on the dependency type and lag duration. By default, new dependencies are created as Finish-to-Start dependencies with zero lag.

How to Establish a Dependency Between Two Tasks (on Gantt chart)

1. Click your intended taskbar on the Gantt chart
2. Click and hold the blue circle to the right or left of the task
3. Drag the blue circle to the dependent task

When creating new dependencies with the taskbar grab handles, pay attention to which handle you’re selecting. From the predecessor task, using the left handle will create a Start-to-XXX dependency, and the right handle will create a Finish-to-XXX dependency. Connecting to the left side of the successor task will create an XXX-to-Start dependency, and connecting to the right side will create an XXX-to-Finish dependency.

Managing Dependency Types and Lag Duration

Once you’ve established a dependency between two tasks, you can edit the dependency’s type and lag time.

How to Change a Task’s Dependency Settings (in sheet)

1. Click on the cell in a task’s Predecessor column
2. Click the Dependencies icon to the right of the Related row value
3. From the Predecessors dialog, select the “Predecessor Type” and specify the “Lag” value
4. Click the blue Close button in the bottom right corner of the dialog

How to Change a Task's Dependency Settings (on Gantt chart)

1. From the Gantt chart, click on a taskbar to open the event dialog
2. Click the blue Manage Predecessors button at the bottom of the dialog
3. Make adjustments to the task’s dependencies in the Predecessors dialog as needed

Lag durations can be expressed as days or hours. Lag can be expressed with positive, zero, or negative values.

Learn more about dependency types and lag duration in our article Introduction to Dependencies.

Note that as you change a task’s dependency settings, the task’s dates may change automatically to reflect the new criteria. Some of these changes can be avoided by enabling and using task constraints.

Removing Dependencies

To remove a dependency between tasks, delete the Related row value in a task’s Predecessor column. Or, from the Predecessors dialog, click the x icon to the right of a dependency. Or, from the Gantt chart, click the dependency arrow and click the X icon that appears.

Dependency Violations

If you schedule or reschedule tasks in a way that violates dependency rules that have been created, the relevant dependency lines on the Gantt chart will be highlighted red.